1. Field of the Invention
The present invention relates to an information reproducing apparatus and method, and more particularly, to an information reproducing apparatus and method for reproducing AV (audio Visual) data recorded on an information recording medium rotationally driven, such as a CD-ROM disc, a CD-R disc or a CD-RW disc.
2. Description of the Related Art
An effort has been made to improve the read rate of an information reproducing apparatus that reads information from an information medium rotated, such as a CD-ROM disc, CD-R disc or a CD-RW disc. On the other hand, such an information reproducing apparatus has problems to be resolved, such as noise because of high-speed rotation of the disc and power consumption.
For example, as the data read rate goes up, noise caused by vibration due to rotation and power consumption become more conspicuous at the time of reproducing AV data recorded on a music CD (CD-RA), a video CD or CD as a WAV file or MP3 file through USB speakers installed in a computer. The WAV file is a most popular audio file format handled by Windows that is an OS of Microsoft and has an extension xe2x80x9cwavxe2x80x9d. The MP3 file is the name of a standardized audio compression technique and has an extension xe2x80x9cmp3xe2x80x9d, wherein MP is an abbreviation of MPeg audio layer 3.
There is an increased possibility that data may be erroneously read more frequently due to crack or dusk as the disc rotates faster.
However, generally, AV data recorded on a disc such as music data, video data and WAV data, is reproduced at an average transfer rate approximately equal to a single multiple. MP data is reproduced at an average transfer rate approximately equal to one tenth of that for AV data. That is, it takes a much longer time to read AV data and MP data than ordinary data. This does not need to rotate the disc fast.
An improved information reproducing apparatus directed to resolving the above problems has been proposed. In the improved apparatus, data that does not need an error correction mechanism, such as music CDs and some video CDs, is read at a given lowered reproduction rate. However, since the reproduction rate is lowered unconditionally, data cannot be read fast in data ribbing or a similar situation required to read data fast. An error correction function is added to WAV data and MP3 data, which will be subject to high-rate read operation in the above-mentioned proposal. Thus, WAV data and MP3 cannot be read at the given lowered reproduction rate.
Japanese Unexamined Laid-Open Publication No. 2000-132901 proposes a disc apparatus capable of controlling the read rate. The proposal shown in this publication analyzes a disc revolution corresponding to the transfer rate of a file to be read, more specifically, the type of data (such as type of file and file size), and thus determines the optimal read rate. The proposal avoids necessity of a requirement for always reading data at the maximum rate, and is therefore preferable in terms of read rate, vibration/noise and power consumption when totally viewed.
However, the technique disclosed in the above publication does not satisfy a request such that the same file is read at different reproduction rates because the unique disc revolution (read rate) is automatically defined based on the type of data to be read (type of file or file size). For example, the proposed technique does not meet different requests for reading data of the same WAV file (for example, WAV reproduction and data ribbing).
It is an object of the present invention to provide an information reproducing apparatus method and apparatus using an information recording medium that is driven rotationally, wherein data can be read at a data transfer rate based on a user""s read request.
The above object of the present invention is achieved by an information reproducing method and apparatus described below.
According to a first aspect of the present invention, an information reproducing method comprises the steps of: reading information from an information medium that is rotated; and determining a rotation velocity of the information medium on the basis of a data transfer rate based on a specification of a read request. Similarly, an information reproducing apparatus comprises: a motor rotating an information medium; an optical pickup reading information from the information medium; and a part determining a rotation velocity of the information medium on the basis of a data transfer rate based on a specification of a read request.
The transfer rate at which data is read is based on the specification of the read request which may be supplied from a user. The data read rate is defined by a rotation velocity of the information medium. The higher the rotation velocity, the higher the read rate, and the lower the rotation velocity, the lower the read rate. Thus, by determining the rotation velocity in accordance with the data transfer rate based on the specification of the read request, the rotation velocity of the information medium may be lowered in a case that a low data transfer rate is acceptable, for example, a case where AV data is retrieved. This avoids reading data at an excessively high bit rate and contributes to reduction of noise and power consumption because of high-speed rotation. Even for AV data, if it is requested to data in ripping, the rotation velocity may be raised to the upper limit. Thus, data can be read at the maximum bit rate.
According to a second aspect of the present invention, an information reproducing method comprises the steps of: reading information from an information medium that is rotated; and measuring an average transfer rate in data read and lowering a rotation velocity of the information medium if the average transfer rate measured is equal to or lower than a predetermined threshold value. Similarly, an information reproducing apparatus comprises: a motor rotating an information medium; an optical pickup reading information from the information medium; a measuring part measuring an average transfer rate in data read; a comparing part comparing the average transfer rate measured with a predetermined threshold value; and a rotation velocity control part lowering a rotation velocity of the information medium by the motor if a result of comparison shows that the average transfer rate measured is equal to or lower than a predetermined threshold value.
Although the second aspect of the invention is basically the same as the first aspect thereof, the second aspect may be preferably applied to a specification of the read request in which AV data such as music CD is retrieved. In such retrieval, the average transfer rate of reading data is much lower than that in ordinary data read. Thus, the average transfer rate is measured and is compared with the predetermined threshold value. If the average transfer rate is equal to or lower than the predetermined threshold value, the rotation velocity is lowered. Thus, AV data such as music CD can preferably be read.
According to a third aspect of the present invention, an information reproducing method comprises the steps of: reading information from an information medium that is rotated; and measuring an average transfer rate in data read and raising a rotation velocity of the information medium if the average transfer rate measured is greater than a predetermined threshold value. Similarly, an information reproducing apparatus comprises: a motor rotating an information medium; an optical pickup reading information from the information medium; a measuring part measuring an average transfer rate in data read; a comparing part comparing the average transfer rate measured with a predetermined threshold value; and a rotation velocity control part raising a rotation velocity of the information medium by the motor if a result of comparison shows that the average transfer rate measured exceeds a predetermined threshold value.
Although the third aspect of the invention is basically the same as the first aspect thereof, the third aspect may be preferably applied to a specification of the read request in which AV data such as music CD is ripped. In such a specification, it is required that data is read at a high average transfer rate. Therefore, the measured average transfer rate exceeds the predetermined threshold value, the rotation velocity of the information medium is raised, so that data can be ripped at a high bit rate.
According to a fourth aspect of the present invention, an information reproducing method comprises the steps of: reading information from an information medium that is rotated; measuring an average transfer rate in data read and raising a rotation velocity of the information medium if the average transfer rate measured is greater than a predetermined threshold value; and lowering the rotation velocity if the average transfer rate is equal to or lower than the predetermined threshold value. Similarly, an information reproducing apparatus comprises: a motor rotating an information medium; an optical pickup reading information from the information medium; a measuring part measuring an average transfer rate in data read; a comparing part comparing the average transfer rate measured with a predetermined threshold value; and a rotation velocity control part lowering a rotation velocity of the information medium by the motor if a result of comparison shows that the average transfer rate measured is equal to or lower than a predetermined threshold value and raising the rotation velocity if the result of comparison shows the average transfer rate measured exceeds the predetermined threshold value.
There is a case where the user requests to alternately read reproduction of AV data and ripping thereof from the same information medium. The average transfer rate is constantly measured while data is being read, and the rotation velocity of the information medium is switched to the low-speed side or high-velocity side with respect to the threshold value serving as a boundary. Thus, the information medium is rotated at a low velocity in retrieval of AV data and is rotated at a high velocity in ripping of data. It is therefore possible to suppress occurrence of a problem such as noise and read error in reproduction of AV data and rip data at a high bit rate.
According to a fifth aspect of the present invention, the information reproducing method may be configured so that it further comprises the steps of: monitoring whether the read request is issued; and restarting measurement of the average transfer rate if the read request is not issued for a predetermined time in measurement of the average transfer rate. The apparatus may be configured similarly.
The measurement of the transfer rate is performed without discriminating AV data files and ordinary data files over each other. In order to avoid reading an ordinary data file at a lowered bit rate or avoid interruption of sound or video because of changing the bit rate to the maximum rate during reproduction of AV data, it is necessary to accurately measure the average transfer rate of reading data. For example, in a case where a read request from the user is temporarily interrupted and ripping of data is restarted in the reading of an ordinary data file, there is a tendency for the measured average transfer rate to be lower than the actual rate. In this regard, generally, the read request from the user tends to be periodically issued at the time of retrieving AV data. This may be a factor for determining whether AV data is being reproduced. That is, the AV data read request is periodically issued to some extent, although this depends on how an application reads data. On the other hand, generally, ordinary data file is read at random and irregularly. In addition, the read process is interrupted when the user does not operate. With the above in mind, the reading is deemed to be the reading of an ordinary data file if the read request is not issued for the predetermined time, and the measurement of the average transfer rate is restarted. This improves the precision of measurement. It is therefore possible to avoid interruption of sound or video because of changing the rate to the maximum level during retrieval of AV data. That is, it is possible to appropriately distinguish reproduction of AV data files over reproduction of ordinary data files.
According to a sixth aspect of the invention, the information reproducing method may be configured so that it further comprises the steps of: monitoring a read address of the read request; and restarting measurement of the average transfer rate if the read address is arranged in a formation other than an increasing order. The information reproducing apparatus may be configured similarly.
The measurement of the transfer rate is performed without discriminating AV data files and ordinary data files over each other. In order to avoid reading an ordinary data file at a lowered bit rate or avoid interruption of sound or video because of changing the bit rate to the maximum rate during reproduction of AV data, it is necessary to accurately measure the average transfer rate of reading data. For example, in a case where a read request from the user is temporarily interrupted and ripping of data is restarted in the reading of an ordinary data file, there is a tendency for the measured average transfer rate to be lower than the actual rate. In this regard, generally, in reproduction of AV data, the read address in the read request from the user is arranged in the increasing order. This may be a factor for determining whether AV data is being reproduced. With the above in mind, the reading is deemed to be the reading of an ordinary data file if the address is not arranged in the increasing order, and the measurement of the average transfer rate is restarted. This improves the precision of measurement. It is therefore possible to avoid interruption of sound or video because of changing the rate to the maximum level during retrieval of AV data. That is, it is possible to appropriately distinguish reproduction of AV data files over reproduction of ordinary data files.
According to a seventh aspect of the present invention, the information reproducing method may be configured so that it further comprises the steps of: determining validity of the average transfer rate on the basis of average transfer rates obtained a number of times of measurement; and validating the average transfer rate if the average transfer rates obtained a number of times of measurement are close to each other. The information reproducing apparatus may be configured similarly.
There is a specific application in which, when the user designates a reproduction skip during retrieval of AV data at a low rotation velocity, data involved in the skip is read at one time and is stored in a buffer memory of a host. In such an application, the average transfer rate will be temporarily raised so that the rotation velocity is unwillingly raised to the maximum level whereby sound of AV data may be interrupted or video may be stopped. In this regard, the average transfer rates of one set obtained by measurement performed several times are nearly equal to each other, the average transfer rate (which may, for example, be one of the nearly equal rates) is validated. That is, the valid average transfer rate is defined based on condition that the average transfer rates obtained several times are close to each other. This improves the reliability of the average transfer rate and copes with a temporary change of the transfer rate such that the average transfer rate is temporarily raised due to the application.
According to an eighth aspect of the present invention, the information reproducing method may be configured so that a first threshold value which is one of said predetermined threshold value and is used for raising the rotation velocity of the information medium is greater than a second threshold value which is another one of said predetermined threshold value and is used for lowering the rotation velocity of the information medium. The information reproducing apparatus may be configured similarly.
There is a possibility that lowering and raising of the rotation speed of the information medium may be repeatedly performed at the time of reading at a transfer rate close to the threshold value although the data transfer rate requested by the user is close to the threshold value for switching the rotation velocity of the information medium. This possibility can be avoid by setting the first threshold value greater than the second threshold value.
According to a ninth aspect of the present invention, the information reproducing method may be configured so that it further comprises the steps of: temporarily storing information read from the information medium in a cache memory; pre-reading information if a space is available in the cache memory; and causing measurement of the average transfer rate to be initiated when the cache memory is full of data and the pre-reading of information is completed in a case where information is read from the information medium at a maximum rate.
In a case where information is read at the maximum rate, measurement of the average transfer rate is started at the time when a cache memory becomes full of data and the data pre-reading process is completed. It follows that there is no need to measure the average transfer rate meaninglessly while information is being read at the maximum rate and that degradation of the performance in the read process can be avoided. At the time of reproducing AV data or the like, the average transfer rate is originally low, and the pre-reading process is completed after the cache memory is full of data. Hence, measurement of the transfer rate is initiated as it stands.